Analysis of the relationship between growth, cephalosporin C production, and fragmentation in Acremonium chrysogenum

Mycelial fragmentation in submerged cultures of the cephalosporin C (CPC) p roducing fungus Acremonium chrysogenum was characterized by image analysis. In both fed-batch and chemostat cultures, the proportion of mycelial clump s seemed to be the most sensitive morphological indicator of fragmentation. In a fed-batch fermentation culture, this declined from roughly 60% at ino culation to less than 10% after 43 h. Subsequent additions of glucose resul ted in a sharp increase back to near the initial value, an increase that re versed itself a few hours after glucose exhaustion. Meanwhile CPC productio n continued to decline steadily. On the other hand, the addition of soybean oil enhanced CPC production, but had no significant effect on the morpholo gy. Although it may sometimes appear that morphology and productivity are r elated in batch or fed-batch cultures, this study suggests that this is bec ause both respond simultaneously to more fundamental physiological changes, dependent on the availability of carbon. In circumstances, such as supplem entary carbon source addition, the relationship is lost. Chemostat cultures supported this belief, as CPC-production rates were hardly affected by the specific growth rate, but the morphology showed significant differences, i .e., lower dilution rates resulted in a lower proportion of clumps and in s maller clumps.